Low idle RPM during deceleration and at a stop
09-09-2009, 08:05 PM
#1
Go Texas Longhorns!
Thread Starter
Low idle RPM during deceleration and at a stop (Dirty Throttle Body?)
I've done a bit of searching and I think I know the answer, but I want to be mostly sure. I have a '04 RX8, 68K mi, mostly stock other than a K&N filter and high-flow cat. The car is not throwing any CELs and shows ready on my scan gauge. Power seems fine, and driving and cruising seems normal. Mileage has also been good as of late.
For some reason, earlier this week I noticed that after the engine is warm, upon deceleration or while waiting at the stop, the RPM would drop suddenly into the 600-700rpm range and hold in that range before hoping up to 950-1100rpm and settling down. This happens both with and without the A/C running. The car has been idling rougher than normal with the A/C in general. I cleaned the MAF and checked the filter last weekend (prior to the issue, just part of my regular maintenance).
I think the TB is likely dirty. I have cleaned it before, but I'm not sure I did it well enough. As the car is not throwing a CEL, and the car is driving fine other than those instances, I can't think of another cause.
If I should clean the TB, should I remove it this time? Any suggestions on the best way to clean it? I can get TB cleaner, but I don't want to damage the motor on the TB plate. What is the best method for cleaning the TB?
I'm open to other thoughts on what could cause this, and I'd rather fix it myself first before going to the dealer.
For some reason, earlier this week I noticed that after the engine is warm, upon deceleration or while waiting at the stop, the RPM would drop suddenly into the 600-700rpm range and hold in that range before hoping up to 950-1100rpm and settling down. This happens both with and without the A/C running. The car has been idling rougher than normal with the A/C in general. I cleaned the MAF and checked the filter last weekend (prior to the issue, just part of my regular maintenance).
I think the TB is likely dirty. I have cleaned it before, but I'm not sure I did it well enough. As the car is not throwing a CEL, and the car is driving fine other than those instances, I can't think of another cause.
If I should clean the TB, should I remove it this time? Any suggestions on the best way to clean it? I can get TB cleaner, but I don't want to damage the motor on the TB plate. What is the best method for cleaning the TB?
I'm open to other thoughts on what could cause this, and I'd rather fix it myself first before going to the dealer.
Last edited by brillo; 09-10-2009 at 10:21 AM.
09-11-2009, 05:32 AM
#2
I've done a bit of searching and I think I know the answer, but I want to be mostly sure. I have a '04 RX8, 68K mi, mostly stock other than a K&N filter and high-flow cat. The car is not throwing any CELs and shows ready on my scan gauge. Power seems fine, and driving and cruising seems normal. Mileage has also been good as of late.
For some reason, earlier this week I noticed that after the engine is warm, upon deceleration or while waiting at the stop, the RPM would drop suddenly into the 600-700rpm range and hold in that range before hoping up to 950-1100rpm and settling down. This happens both with and without the A/C running. The car has been idling rougher than normal with the A/C in general. I cleaned the MAF and checked the filter last weekend (prior to the issue, just part of my regular maintenance).
I think the TB is likely dirty. I have cleaned it before, but I'm not sure I did it well enough. As the car is not throwing a CEL, and the car is driving fine other than those instances, I can't think of another cause.
If I should clean the TB, should I remove it this time? Any suggestions on the best way to clean it? I can get TB cleaner, but I don't want to damage the motor on the TB plate. What is the best method for cleaning the TB?
I'm open to other thoughts on what could cause this, and I'd rather fix it myself first before going to the dealer.
For some reason, earlier this week I noticed that after the engine is warm, upon deceleration or while waiting at the stop, the RPM would drop suddenly into the 600-700rpm range and hold in that range before hoping up to 950-1100rpm and settling down. This happens both with and without the A/C running. The car has been idling rougher than normal with the A/C in general. I cleaned the MAF and checked the filter last weekend (prior to the issue, just part of my regular maintenance).
I think the TB is likely dirty. I have cleaned it before, but I'm not sure I did it well enough. As the car is not throwing a CEL, and the car is driving fine other than those instances, I can't think of another cause.
If I should clean the TB, should I remove it this time? Any suggestions on the best way to clean it? I can get TB cleaner, but I don't want to damage the motor on the TB plate. What is the best method for cleaning the TB?
I'm open to other thoughts on what could cause this, and I'd rather fix it myself first before going to the dealer.
but also,
check plug wires, tight..
plug time? 20k miles, done.
coils?
just for fun. pull room fuse and do the brake dance and see what happens..
btw, someone say fuel pump? doubt it, but.
beers
09-11-2009, 12:05 PM
#4
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I've got the EXACT same problem...brake dance didn't help, car has 20k miles on it and I'm assuming the plugs were never changed by the previous owner so I'm in the process of trying that fix. If cleaning the TB works for you, let me know...
09-11-2009, 12:17 PM
#5
Go Texas Longhorns!
Thread Starter
I live, I just lurk 
Work, girls, school take up alot of what was my car time.
I think I need to reconsider this whole adult thing, its overrated....
Work, girls, school take up alot of what was my car time.
I think I need to reconsider this whole adult thing, its overrated....
09-11-2009, 03:12 PM
#7
Go Texas Longhorns!
Thread Starter
I've had a compression test done at 59,xxx, it was fine. If I was having compression issues I woul have mileage / power drop off me thinks.
09-13-2009, 03:23 PM
#8
Go Texas Longhorns!
Thread Starter
cleaning the TB and resetting the computer seems to have fixed the issue at this point, I'll watch it this week to be sure as it has not completed all the drive cycles necessary to show ready on my scan gauge.
09-13-2009, 05:58 PM
#9
My 8 looks like a Smurf
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Let me know if your problem returns. I have the same problem (had it for a while) and today I had this problem.
Thinking they might be related.
Thinking they might be related.
09-14-2009, 11:28 AM
#11
I dont know if this has anything to do with it...but I just put Borla Exhaust on my car yesterday. My car is doing close to the same thing, except it just dies instead of hopping back up. It runs perfectly, no rough idle or anything, except after I have driven it for awhile, when I'm coasting up to a stop sign, it will just die.
It had never done it before I put the exhaust on it, and then it did it like...10 times or so the same day.
Is this normal after you put new exhaust on at first? Or would you guys suggest doing the same checks you have told Brillo? I was getting ready to search it, but found this post was still alive so I thought I would ask here first.. Thanks.
It had never done it before I put the exhaust on it, and then it did it like...10 times or so the same day.
Is this normal after you put new exhaust on at first? Or would you guys suggest doing the same checks you have told Brillo? I was getting ready to search it, but found this post was still alive so I thought I would ask here first.. Thanks.
nice to see you around!
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